Flexible display technology is a forward-looking technology which is popular in recent years, and a flexible display device is light and thin, bendable and even curlable and good in mechanical properties, thus attracting more and more attention of people. The flexible display device includes a display substrate, wherein the display substrate includes a base substrate and a structure on the base substrate, the base substrate is a flexible base substrate, for example, a polyimide (PI) base substrate, a polyethylene glycol terephthalate (PET) base substrate, a stainless steel base substrate and the like, compared with an ordinary glass base substrate, the flexible base substrate has the characteristic of bendability, and this proposes higher requirements on the reliability of devices and especially vulnerable members.
Stress aggregation will be generated during bending, and with the increase of the number of bending operations, various vulnerable members on the flexible base substrate of the flexible display device are liable to be damaged. For example, due to the stress aggregation during bending, the film layers of the thin film transistor (TFT) as a vulnerable member are likely to be fractured, which will affect the performance of the TFT and thus affect the reliability of the flexible display device. Therefore, how to avoid the damage to the vulnerable members due to stress is very important for the reliability of the flexible display device.